A new study in Nature reveals that the spines in male chimpanzee’s members increases stimulation during sex. Humans also once had penile spines, although evolution rid both us and Neanderthals of that little trait.

While it’s proposed that these spines increase stimulation for males and females, it seems the male chimps have the better end of the stick as the spines may cause damage to females during intercourse.

The study compared human, Neanderthal and chimpanzee genomes. Neanderthals, like humans, dropped the trait long ago, leading researchers to believe the two species would have happily mated.